I think that Irenicus in theory *could* romance a human, but it would have to be rather difficult. As in, you have the say the EXACT right thing, no if ands or buts. Also, I think the intelligence/wisdom requirement would have be exceptionally high, maybe even 16 or so. I think that a half-elf would almost be more difficult that a human, half-breeds are looked down upon quite badly. Really though, since the char is a Bhaalspawn, I think that would make up for the human-ness. Maybe something in the end could grant the char immortality, if she agrees to stay human? Just a thought...already done by Lord E I do believe, in RtR.
Sorry for my silence - I was feeling a little bit down these last few days. But I am still working on this project and have no intention of abandoning it. In fact you may see more posts here soon.
About raising the intelligence and wisdom limits to 16 - good point - but won't this be an overkill? On the other hand I cannot see anybody in their sane mind romancing Jonny casually, so either you have a character to fit (or create one) or you don't . Since all my chars have int 18+ ( and charisma 6-7) I have no problem with this. Most of the romance is going to be rather extensive discussions on the matters far too serious to be any fun for char <16 int.
Immortality after PC gives up the godhood is another matter. But since Jonny is immortal no longer it may not be a problem. The human romance may have a different flavor though ... we will see.